1. Field of the Invention
This invention relates to check valves. More particularly, this invention relates to check valves having presettable and adjustable cracking pressures.
2. Description of the Background Art
Presently, there exist many types of check valves designed to allow the flow of a fluid such as a gas in one direction but to block or “check” the flow of the fluid in the opposite direction. The amount of fluid force required to open the poppet of the valve in the un-checked direction is often referred to as the cracking pressure. Typically, the cracking pressure of a check valve is determined by the spring constant of the internal spring which constantly urges the poppet into a sealing position until unseated therefrom once the cracking pressure is attained.
A predetermined cracking pressure of a check valve is desired when check valves are used in conjunction with inflatable articles such as life vests and life rafts. Specifically, a check valve having a predetermined cracking pressure allows the inflatable to be inflated by means of a gas cartridge or the like to assure that the inflatable is inflated to a preset internal pressure. Thus, by allowing excess gas to be exhausted, over-capacity gas cartridges can be employed to inflate the inflatable to ensure that the inflatable is fully inflated to a preset internal pressure in all environments.
Whereas in some applications a preset cracking pressure is desired, in other applications it is desirable to have a check valve with a variable cracking pressure. A check valve with a variable cracking pressure may be desired, for example, in an inflatable device such as a life vest to achieve a certain amount of buoyancy or when a certain rigidity is desired. Further, in still other applications such as when transporting an inflatable, it is desirable to be able to “lock” the check valve from opening irrespective of the amount of cracking pressure in the inflatable. Finally, it may be desirable in still other applications to be able to manually open the check valve to quickly “dump” air from an inflatable. Thus, there presently exist various needs in the check valve industry for a check valves with fixed cracking pressures, with variable cracking pressures, with a locking feature and/or with a dumping feature.
Therefore, it is an object of this invention to provide an improvement which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the check valve art.
Another object of this invention is to provide a check valve having an increased flow rate.
Another object of this invention is to provide a check valve having a structure composed of a minimal number of parts to increase its reliability while decreasing cost of manufacture and assembly.
Another object of this invention is to provide a check valve having a design that equalizes the sealing force of the poppet around its entire periphery to assure that the check valve is cracked uniformly about the periphery of the poppet.
Another object of this invention is to provide a check valve with a fixed cracking pressure.
Another object of this invention is to provide a check valve with a with a variable cracking pressure.
Another object of this invention is to provide a check valve with a locking feature to prevent cracking of the check valve irrespective of the pressure exerted that would otherwise crack valve open.
Another object of this invention is to provide a check valve with a manual dumping feature that allows the valve to be manually cracked open.
The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.